This invention relates to improvements for heated insoles for shoe wear, especially for hiking, cycling and skiing and even for ordinary shoes if the wearer has cold feet.
Over the years, various systems have been designed and employed to provide additional heat inside shoes when they are used in outdoor environments. An example of such a prior art system is shown in US Patent Publication US2009/0013554, which is directed to a wireless system in which signals are transmitted to control a heater in the insole.
For some time, there have been fixed hardwired systems such as shown in U.S. Pat. No. 4,665,301 in which heaters are plugged into a wall socket to provide heat to the insole which is used during the day. It may be recharged through a suitable recharging system to reheat the heated insole to provide sufficient warmth to the user.
These systems generally have an electric heater placed on the bottom of the insole with various nonconductive foam materials therein. Current designs, while conventional, are limited in that a good portion of the heat is not provided to the upper portion of the sole, which is in closer contact with the foot of the wearer.
Lithium ion batteries which are flat have been incorporated as the batteries to provide power for the insole, and opposed to having battery power outside the boot as was previously provided for heating the insole.
Lithium ion battery chargers are generally formed of two sections:                A power supply that converts line AC into low voltage DC; and        An intelligent circuit (IC) that receives the low voltage DC, monitors the battery charge state, and delivers suitable current and voltage to fully and safely charge the batteries for heating the heating pad and the insole.        
Heretofore insoles with built in lithium ion batteries have the charger power supply as a wall mounted device and the intelligent charging circuit located inside the insole. This arrangement subjects the charging components to the heat and mechanical stress of use when the footwear is worn. Any failure of a charging component renders the entire product useless.
An object of this invention is to provide an improved heating system for insoles for shoes.
Another object of this invention is to more efficiently provide heat to the wearer during normal usage.
Another object of this invention is to provide an improved lithium battery system in which the intelligent circuit component is located outside the shoe.
Yet another object of this invention is to provide a more efficient, economical system for heating insoles.
Another object of this invention is to more efficiently locate the heater within an insole to more directly provide heat to the foot of the wearer.
Yet another object of this invention is to provide a more efficient and economical battery charging system more susceptible of widespread use.
Other objects, advantages and features of this invention will become more apparent from the following description.
In accordance with the principles of this invention, the above objects are accomplished by separating the intelligent circuit (IC) which charges the rechargeable lithium batteries from the lithium ion batteries itself. This may be accomplished by locating the IC charging circuit within the AD/DC plug adapter assembly or having the IC charging circuit assembly as a module closely located and connected to the AC/DC converter.
Since the IC is a relatively expensive part of the lithium battery assembly, removing it from the physical wear and tear conventionally encountered and integrally formed with the battery to be charged enables a costly component to prolong its life, reduce the possibility of failure and ensure that only the lithium battery is replaced when necessary without the need to replace the entirety of the Intelligent Circuit (IC) lithium battery combination.
Further, the above objects are accomplished by additionally relocating the heater within the insole from the substantially bottom most location furthest from the foot of the user to a location closer to the foot of the user so as to provide more efficient heat directed to the user, thereby reducing power drain and more efficiently and quickly heating the area. Prior art insoles have an EVA foam layer of about 5 mm thickness located above the heater. The new structure compresses the EVA foam to no more than 2 or 3 mm, then adds an additional conductive layer above the battery and an additional insulating layer between the foot and bottom of the shoe to improve heat conductivity to the foot of the wearer.
These improvements are described below in greater detail with reference to the following drawings.